Japanese Patent No. 2655774 discloses a column base structure. In this column base structure, a base plate is fastened to anchor bolts that are fixed to a foundation, and an H-section steel column is attached to an upper face of the base plate through inverse T-shaped split tees. Upright plate portions of the split tees are fastened to the column using high strength bolts and nuts, and bottom plate portions of the split tees are fastened to the base plate similarly using high strength bolts and nuts.
In the above column base structure, tensile stress arises in the anchor bolts on the stress-imparted side when for example bending stress is imparted to the column in a web width direction. When plural anchor bolts in which web width direction tensile stress arises are provided, the greatest amount of yield deformation arises in the outermost anchor bolt(s). Since the yield bending capacity of the column base structure is determined by the outermost anchor bolt(s) regardless of the yield deformation of inside anchor bolts, there is accordingly room for improvement in raising the yield bending capacity of the column base structure.